1. Field of the Invention
The present invention is directed to a subkerationous electroencephalographic (EEG) probe and, more particularly, to a self-preparing probe which penetrates an electrically insulating keratinous cuticle layer or dead layer of skin and contacts the blood rich epidermis layer under the keratinous layer and which is useful in an evoked potential autorefractometry system for prescribing eyeglass lenses.
2. Description of the Related Art
Prior art EEG electrodes are not self-preparing electrodes in that hair, along with the electrically insulating keratinous layer of skin, must be removed before application of the electrode by shaving the hair and abrading the skin until it is raw with an abrading tool or an electrolyte cream which includes an abrading grit. FIG. 1 is an example of a prior art stick-on EEG electrode 10 which includes an adhesive 11 for sticking an insulating plastic body 12 to the skin and which can be obtained from Beckman Instruments, Shiller Park, Ill. The insulating plastic body 12 has included therein a metal conductor or slug which forms a cavity 14. The cavity 14 is filled with electrolyte cream after the skin has been abraded and before application of the electrode to the skin. A wire 15 connects the metal conductor 13 to the measurement apparatus. FIG. 2 is another example of a prior art electrode 20 which is attached to a piece of flexible cap fabric 21 by a press-fit gromet 22. This electrode 20 also forms a cavity 23 using an insulating plastic body 24 and metal conductor 25. The metal conductor 25, insulating plastic body 24, fabric 21 and press-fit gromet 22 include an injection hole 26 through which a blunt syringe needle is inserted. The blunt needle is used as a scraping tool to remove the dead layer of skin and then inject an electrolyte cream into the cavity between the skin and metal conductor 25. Further details of electrode 20 and the cap fabric 21 to which it is attached can be found in U.S. Pat. Nos. 4,323,076 and 4,085,739.
As discussed above, the prior art electrodes are non-self-preparing electrodes requiring that the hair be cut and the skin be abraded to remove the dead layer of skin before the electrodes can be properly applied. As a result, the prior art electrodes are not desirable in commercial applications where the patient visits the establishment only for a short time.